Author: rmacklem
Date: Sat May 7 02:00:35 2011
New Revision: 221570
URL: http://svn.freebsd.org/changeset/base/221570
Log:
MFC: r220967
Fix a LOR in vfs_busy() where, after msleeping, it would lock
the mutexes in the wrong order for the case where the
MBF_MNTLSTLOCK is set. I believe this did have the
potential for deadlock. For example, if multiple nfsd threads
called vfs_busyfs(), which calls vfs_busy() with MBF_MNTLSTLOCK.
Thanks go to pho for catching this during his testing.
Modified:
stable/8/sys/kern/vfs_subr.c
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/amd64/include/xen/ (props changed)
stable/8/sys/cddl/contrib/opensolaris/ (props changed)
stable/8/sys/contrib/dev/acpica/ (props changed)
stable/8/sys/contrib/pf/ (props changed)
Modified: stable/8/sys/kern/vfs_subr.c
==============================================================================
--- stable/8/sys/kern/vfs_subr.c Sat May 7 01:05:31 2011
(r221569)
+++ stable/8/sys/kern/vfs_subr.c Sat May 7 02:00:35 2011
(r221570)
@@ -380,9 +380,10 @@ vfs_busy(struct mount *mp, int flags)
if (flags & MBF_MNTLSTLOCK)
mtx_unlock(&mountlist_mtx);
mp->mnt_kern_flag |= MNTK_MWAIT;
- msleep(mp, MNT_MTX(mp), PVFS, "vfs_busy", 0);
+ msleep(mp, MNT_MTX(mp), PVFS | PDROP, "vfs_busy", 0);
if (flags & MBF_MNTLSTLOCK)
mtx_lock(&mountlist_mtx);
+ MNT_ILOCK(mp);
}
if (flags & MBF_MNTLSTLOCK)
mtx_unlock(&mountlist_mtx);
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